There has been a long-felt need for an effective and durable seal around the rear doors of a semitrailer. In the course of transporting cargo over long distances, semitrailers are exposed to severe weather and other environmental conditions that cause deterioration of door seals. The semitrailers are also prone to the buildup of dirt and road salt, resulting in abrasive wear of the seals, and are constantly subjected to door frame movement, or racking, that causes movement between the door seals and adjoining surfaces. Heretofore, semitrailer door seals have typically been lip-type seals formed of polyvinyl chloride or similar thermoplastic material.
In an attempt to provide better seals, some arrangements have proposed the use of a compression seal in addition to a lip seal. For example, U.S. Pat. No. 5,107,622 issued Apr. 28, 1992 to Fuchs et al describes a door seal assembly that has two elements. The outer element is a double lip seal, whereas the inner element, in one embodiment, is a compression seal.
Compression seals provide a biased seal against an adjacent opposed surface that is generally better, and tighter, than that provided by a lip seal. However, because of their inherent construction, compression seals tend to be undesirably displaced, or distorted, at their corners when the door they are sealing is closed. The excessive distortion of the compression seal at the corners leads to early failure of the seal, requiring replacement.
The present invention is directed to overcoming the above problems. It is desirable to have a door seal that has a lip seal that overlays adjoining outer surfaces, and a compression seal that is compressed against an adjacent opposed surface. Furthermore, it is desirable to have such a seal that avoids the problem of undesirable compression seal distortion at the seal corners. It is also desirable to have such a seal that is formed of a abrasion- and weather-resistant, long wearing elastomeric material.